Topband: Inverted ELL for 160M

Jerry Keller k3bz at arrl.net
Wed Nov 3 14:09:13 EST 2004


Many thanks to those who responded to my question with some good comments and ideas. Almost everyone 
said I should use radials on the ground rather than elevated, but I think I have to stick with the 
two elevated radials to start with due to physical constraints onsite. But I'll keep the advice in 
mind and try to figure a way to do ground radials next summer. It will be an interesting comparison.

I must apologize for not mentioning in my earlier post that the idea of using a pair of 1/4 wl 75 
ohm feedlines in parallel was something I read by Tom, W8JI.

The line impedence of two paralleled 1/4 wl 75 ohm lines is 37.5 ohms, which inverts to 56.25 ohms 
at the transmitter end and provides a 1.13 :1 match to 50 ohms. Does the line impedence of 37.5 ohms 
also invert to 56.25 ohms for other odd multiples of 1/4 wl...i.e., 3/4 wl, 5/4, etc....???

Also, would such a transmission line transformer arrangement benefit from coiling the extra doubled 
coax into a choke at the feedpoint? If so, how many turns/diameter would make it effective?

Last, I have a spool of RG59/U CATV coax with stranded center conductor and double shield.....tinned 
braid plus a foil under the braid that seems like it's glued onto the soft white dialectric. It's 
marked  "Omnicable P/N E15901 RG59/U  E82833 20 AWG 75*C (UL) Type CL2 OR CATV". Will this stuff do 
the job? How much power will a paralled pair handle? And what would be its Velocity Factor?

73,  Jerry K3BZ





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